Charles e



(N0 Model.)

C. E. bCRIB1\IER.` TELEPHONE EXCHANGE.

No. 481,679. Patented Aug. so, 1892.

UNITED STATES PATENT EEICE.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGN OR TO THE IVESTERN ELECTRIC COMPANY, OF SAME PLACE.

TELEPHONE-EXCHANGE.

SPECIFICATION forming part of Letters Patent No. 481,679, dated August 30, 1892.

Application filed November 16, 1891. Serial No. 411,981l (No model.)

To ctZZ whom t may concern:

Be it known that I, CHARLES E. SCEIBNER, a citizen of the United States, residing at Ohicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Telephone-Exchange Apparatus, (Case No. 242,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying 1o drawings, forming a part of this specification. My invention relates to telephone-exchange apparatus, and more particularly to the operators outfit at the central office.

My invention has reference to those systems of telephone-exchange in which the branches or limbs of the different lines are connected with the springs of the switch or switches and thence through the individual annunciator. zo My invention will be shown in connection with a multiple-switchboard system in which metallic circuits are employed, the telephonelines being normally grounded at the subscribers station and permanently grounded at the central oiiice. The individual annunciator of each line is provided with two electro-magnets, the respective coils thereof being in different limbs or branches of the line, These electro-magnets when energized exert 3o opposite pulls upon the common armature, so that when both are energized the annunciator will not be thrown down. Vhen, however, the electro-magnet whose coil is in that limb of the circuit connecting with the springs of 3 5 the switches is alone excited, the individual annunciator will be operated. In case the electro-magnet in the limb of the telephoneline connecting with the test-rings is alone excited the individual annunciator will not 4o be operated, since the pull or attraction of this electro-magnet is in a direction to prevent the annunciator from being thrown down. Metallic circuits th us connecting with multiple switchboards and with individual annunciators having each two oppositelyacting electro-magnets I have shown and described in my application, Serial No. 397 ,900, filed June 29, 1891, for multiple-switchboard systems. The electro-magnet of the individual annunciator which is included in the limb connecting with the springs of the switches I term the operating electro-magnet, as distinguished from the other electromagnet, whose coil is included in the branch or limb of the line connecting with the testpiece of the switches.

Speaking generally, my invention consists in the operators keyboard circuit and apparatus. One strand of the pair of cords, preferably that, connected with the sleeves of the 6o plugs, being provided with a branch circuit through battery to ground, the other strand of the cords, that connecting with the tips of the plugs,being provided with bridge-wires to the other strand, one bridge-wire including the operators telephone, the other including the clearing-out drop and a condenser.

The operators telephone has been heretofore commonly connected or bridged between the cords as shown herein. The clearing- 7o out drop has also been connected in another bridge-Wire; but no condenser has been used in the bridge-wire including the clearing-out drop. The battery with which the sleevestrand of the cord is connected should be of, say, fifteen volts, the primary function of this battery being t-o supply current to the retaining electro-magnet ofthe individual annunciator of a line with which connection has been made. I therefore have termed the bat- 8o tery a retaining-battery, although it is adapted to serve also as a test-battery. A testbattery, however, would not require as much electro-motive force, four or five volts being sufficient for testing purposes. rlhe bridgewire containing the operators telephone will be ordinarily open while a conversation is going on between two subscribers. The bridge-Wire containing the clearing-out aununciator must be closed to signaling-cur- 9o rents sent over the lines from either subscribers station. These currents being alternating currents, it follows that they will be effective to throw down the clearing-out drop, notwithstanding the condenser, which is in- 9g eluded in circuit with the drop. Current from the retaining-battery, however, will not be eiective to operate the clearing-out drop, on account of the said condenser, nor can current from the retaining-battery find circuit roo through the bridge-wire containing this condenser to the tipstrandthat is, the strand connecting the tips of the plugs-and hence current from the retaining-battery is prevented from fiowing through the coil of the operating electro-magnet of the individual annunciator of aline with which either of the pair of plugs has been connected. I preferably place a condenser iii the tip-strand of the cord ina well-known way to make the test more certain when my system is applied to multiple switchboards. The"u retaining-battery may be common to a large number of cords, a sleeve-strand of each cord having a separate branch or third leg connection extending from each sleeve-strand to the battery and ground. I preferably include in each of these third-leg connections a retardation -coil, the retardation-coils performing their well-known function of preventing crosstalk as between the different cords and loss of voice-currents to ground, while permitting a flow of current to the cord.

My invention will be more readily understood by reference to the accompanying drawing, which is a diagrammatic illustration of two multiple switchboards, two subscribers stations connected therewith, an the operators keyboard apparatus at the different switchboards. It will be seen that the telcphoue-line a extends from station l in two branches or limbs, the limb a being connected with the spring of the switches b and c of this line on the dilerent boards, and extending thence through the coil of the operating electro-magnet d of the individual annunciator of the line and thence to ground. The other limb a2 of line o, extends through the test-pieces of said switches b c, thence through the coil of the retaining electro-magnet e of the said individual annunciator, and thence to ground. The answering-jack f of line a is included in the circuit thereof in the usual way at the second board. Subscribers station 2 is connected by line g with spring jack-switches h il on the two boards and with the answering-jack 7c, thence through the operating electro-inagnet lof the individual annunciator, and thence to ground. The testcircuit m of this line is connected from the ground at the central oilice through resistance m', and thence with the test-pieces of the switches 7L i 7c, and is provided with a branch connection m2, extending through the retaining electro-magnet m3 of the individual annunciator and thence to ground. It will be observed that t'est-wire m of line g, instead of continuing to the subscribers station, passes to ground through resistance m. If test-wire m extended to station 2, the circuit of the line of station 2 would be the saine as that of station 1.

I will now describe the operators out-fit at the different switchboards somewhat in detail. Thus, as shown at board 1,.the tips of the plugs nn are connected together by strand n2, while the sleeves of these plugs are connected together by strand n3. The telephone 'n4 is bridged between these cords, and the Cain-lever key 91.5, of usual construction, provided for cutting the telephone out and in, as desired. In the circuit ot' strand n2, between the tips of the plugs, I preferably inciude a a condenser n.5, and usual ringing keys a7 n are provided for looping the generator into circuit between tlie tip and sleeve of the plug, as occasion requires. The clearing-out drop o is included in the bridgewire o between the two strands n2 n3 of the cords. In this bridgewire o', I have placed a condenser 02. The third leg or half-connection o3 extends from the strand n3 through the retardation-coil o, and thence through battery o5 to ground. The operators outfit at the second board is of the same construction. The plug p is shown inserted in answering-jacky". When the plug is thus inserted in the switch of any line, the tip of the plug is connected with the spring of the switch and the sleeve with the testring of the switch. The telephone at station 1 is shown removed from the hook, so that the subscriber may speak to the operator at board 2 when the operator bridges his telephone into circuit. Assuming the telephone at station l to be on the hook, the subscriber 1 by turning his generator will send current over limb a through electro-magnet cl of the 1ndivldual annunciator of line a to notify the operator of board 2 of his call. The operator at board 2 inserts his plug in the answeringjack j of line a, as before described. Current from the battery o5 will now flow through electro-magnet e by a circuit which may be traced from said battery o5 through retardation-coil p', wire p2, branch Wire p3, thence through the calling-key p4, thence by the strand pinto the sleeve of plug p, thence to the test-piece of switch f, thence to limb a2, and thence through the coil of electro-magnet e to ground. The annunciator-drop, therefore, cannot be thrown down by any current which may pass through the electro-magnet d of said individual annunciator.

My invention may be used with systems employing only one switchboard, and other forms of individual annunciators may be substituted Vfor the double electro-magnet individual annunciator shown herein.

Having thus described my invention, I claim as new and desire to secure by Letters Patent- 1. The combination, with the individual aniiiincator provided with two electro-magnets connected in dilerent branches of the subscribers telephone-line, of the clearing-out drop included with the condenser in a bridgewire between the strands of the cords, said cords and their terminal plugs, the retardation-coil in the branch leading to the retaining-battery, and said battery, whereby the individ ual annunciator is prevented from being thrown down when generator-current is sent to line from the subscribers station, while the clearing-out drop is traversed by such generator-current and operated thereby, substantially as described.

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2. The combination, with a battery 05, of yIn witness whereof Ihereunto subscribe my branch circuits 03192, each including a, retardaname this 14th day of November, A. D. 1891. tion-coil and a set of plugs wit-h double-stranded cords for each branch circuit, and a, clear- CHARLES E. SCRIBNER. 5 ing-out annunoiator and a condenser in a Witnesses:

bridge-wire between the strand of each set of GEORGE P. BARTON,

cords, substantially as specified. GEORGE L. CRAGG. 

